Low-power CMOS systems with wireless capability may be utilized in a vast number of applications, such as, for example and without limitation, wireless sensor networks, implantable devices and the future “internet of things” (IoT), to cite a few examples. Though these low-power systems may be designed for various or different applications, they generally share certain similarities, namely, small form factor, low power consumption and large idle time.
Integrating multiple circuit blocks of such systems in a single CMOS chip helps reduce the size of the system. Various circuit techniques, such as, for example, subthreshold operation for digital circuits and current reuse for analog circuits have been proposed to reduce power consumption. To further reduce power consumption, the system may be put into a reduced power consuming mode (i.e., a “sleep” mode) when no task is assigned. More specifically, most power consuming blocks or components of the system, RF transceiver or receiver, are turned “off” during the sleep mode to reduce the amount of power consumed and thus, extend the life of the battery of the system. This, however, poses obstacles on other components of the system that want to communicate with the “sleeping” component (e.g., transceiver or receiver).
One way for overcoming this obstacle is to periodically “wake up” the sleeping device to listen to a communication channel. However, this not only requires an accurate timer to achieve synchronization among components in the system, but also increases latency. Another solution is to use a wake-up receiver (WuRX) that consumes extremely low power to continuously monitor the communication channel and also achieves synchronization between devices. Upon the detection of a “wake-up” signal by the WuRX, the WuRX acts to wake the sleeping component such that it may receive data being communicated to it (i.e., the WuRX may send a one-bit signal to the receiver). This may be accomplished by generating, for example, a single wake-up bit (i.e., a logic “1” or “0”, depending on the particular implementation) that causes the sleeping component to turn “on” or to trigger some other predetermined event(s).
There are many WuRX are known in the art. Some of these focus on the RF front-end design. Indeed, when the power budget for the WuRX is not tight, the RF front-end normally consumes most of the power and determines the performance. However, when the power budget for the WuRX is near or below the microwatt range, the RF front-end is most likely to be implemented as a simple envelope detector followed by a baseband amplifier for down-mixing. In this circumstance, power consumption of the baseband processing circuitry of the WuRX begins to play an important role. Recently, interest has been shown in nanowatt wake-up receivers. For such low-power consumption, the amount of power burned by the baseband processing circuitry of the WuRX is significant, if not dominant.
Accordingly, there is a need for baseband processing circuitry for a WuRX that minimizes and/or eliminates one or more of the above-identified deficiencies.